Charged particle beam pattern transfer apparatus and method

- Nikon

This invention concerns a charged particle beam pattern transfer system which uses a flux of charged particles, e.g. from an electron or ion beam, to transfer a mask pattern to a sensitized substrate. In particular, the invention is applicable to an electron beam reduction transfer system which demagnifies and transfers a mask pattern defined by multiple mask subfields to a sensitized substrate using the step-and-repeat transfer method. The invention provides a system for transferring the mask subfields, separated from one another on the mask by boundary strips, onto a wafer such that the transferred images of the mask subfields are joined together on the wafer as transfer subfields lacking any intervening boundary regions.

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Claims

1. A charged particle beam pattern transfer apparatus for transferring to a substrate a pattern defined by multiple subfields on a mask, the apparatus comprising:

(a) a first main deflector set situated relative to an optical axis of the apparatus, the first main deflector set being operable to deflect toward the optical axis a charged particle beam that has passed through a mask subfield;
(b) an imaging lens system operable to focus the charged particle beam deflected by the first deflector set;
(c) a second main deflector set situated relative to the optical axis, the second main deflector set being operable to deflect, toward a transfer subfield on the substrate corresponding to the mask subfield, the charged particle beam focused by the imaging lens system; and
(d) a first position-correcting deflector set situated relative to the optical axis between either the mask and the first main deflector set or the second main deflector set and the substrate, the first position-correcting deflector set being operable to deflect the charged particle beam and thus correct the position at which the charged particle beam, that has passed through a mask subfield, is incident upon the substrate so as to compensate for any discrepancies in the positions of the transfer subfields relative to each other compared to the positions of the mask subfields relative to each other.

2. The apparatus of claim 1, wherein each of the first and second main deflector sets are moving-trajectory-projection deflector sets.

3. The apparatus of claim 1, wherein the mask subfields are separated from each other by boundary regions, the first position-correcting deflector set being operable to deflect the charged particle beam in a manner whereby the boundary regions are not reproduced between transfer subfields on the substrate.

4. The apparatus of claim 1, further comprising a second position-correcting deflector set, wherein the first position-correcting deflector set is situated between the mask and the first main deflector set and the second position-correcting deflector set is situated between the second main deflector set and the substrate.

5. The apparatus of claim 4, exhibiting a demagnification of 1/.beta. (where.beta. is a real number), wherein the first position-correcting deflector set is operable to displace the beam from the optical axis.beta. times the displacement of the beam from the second position-correcting deflector set.

6. The apparatus of claim 4, wherein each of the first and second position-correcting deflector sets comprises two subdeflectors.

7. The apparatus of claim 6, wherein each of the subdeflectors of the first position-correcting deflector set deflects the beam at equal but opposite deflection angles, and each of the subdeflectors of the second position-correcting deflector set deflects the beam at equal but opposite deflection angles, thereby ensuring the beam exits each position-correcting deflector set at an angle relative to the optical axis that is the same angle by which the beam enters the respective position-correcting deflector set.

8. The apparatus of claim 7, wherein the charged particle beam is incident to the mask perpendicularly to the plane of the mask, and is incident to the substrate perpendicularly to the plane of the substrate.

9. The apparatus of claim 1, wherein the charged particle beam is an electron beam.

10. The apparatus of claim 1, further comprising a second position-correcting deflector set, wherein the first position-correcting deflector set is situated between the mask and the first main deflector set and the second position-correcting deflector set is situated between the second main deflector set and the substrate, each of the first and second position-correcting deflector sets comprising plural subdeflectors axially spaced from each other, the subdeflectors of the first position-correcting deflector set having an axial spacing therebetween that is.beta. times the axial spacing between the subdeflectors of the second position-correcting deflector set, wherein 1/.beta. is the absolute value of the demagnification from the mask to the substrate.

11. The system of claim 10, wherein each of the subdeflectors of the first position-correcting deflector set deflects the beam at equal but opposite deflection angles, and each of the subdeflectors of the second position-correcting deflector set deflects the beam at equal but opposite deflection angles, thereby ensuring the beam exits each position-correcting deflector set at an angle relative to the optical axis that is the same angle by which the beam enters the respective position-correcting deflector set.

12. In a moving-trajectory projection system for transferring a pattern from a mask to a substrate wherein the pattern is subdivided into a plurality of mask subfields each defining a separate portion of the pattern, the mask subfields being separated from one another by boundary regions that do not define any portion of the pattern, and the projection system including a moving trajectory optical system operable to cause a charged particle beam to pass through the mask subfields individually and form the pattern as an ordered assemblage of transfer subfields on a substrate, an improvement, comprising a position-correcting deflector set situated coaxially externally to the moving-trajectory optical system, the position-correcting deflector set being operable to deflect the charged particle beam so as to cause the portions of the pattern defined by the mask subfields to be transferred to the substrate as respective transfer subfields directly contacting each other in a serial manner without any intervening boundary regions.

13. A method for transferring a pattern, defined by plural mask subfields on a mask, each mask subfield defining a portion of the pattern and being separated from one another by boundary regions that do not define any portion of the pattern, from the mask to a substrate, the method comprising:

(a) directing a charged particle beam to pass serially through plural mask subfields;
(b) passing the beam through an optical system operable to deflect the beam sufficiently to cause the beam to be incident on a sensitive substrate so as to form on the substrate transfer subfields corresponding to the mask subfields through which the beam passed;
(c) passing the beam through a first position-correcting deflector set situated coaxially with respect to the optical system and being operable to cause deflection of the beam sufficient to cause the portions of the pattern represented by the transfer subfields on the substrate to directly contact each other in a serial manner without any intervening boundary regions.

14. The method of claim 13, wherein step (c) further comprises passing the beam through a second position-correcting deflector set after the beam passes through the first position-correcting deflector set.

15. The method of claim 13, wherein step (b) comprises passing the beam through an optical system comprising a first MTP deflector set, a second MTP deflector set, an MTP projection lens, and an MTP objective lens.

16. The method of claim 13, wherein the first position-correcting deflector set is arranged relative to the beam to cause the beam to be displaced in a manner by which the beam in incident on the substrate perpendicularly to the substrate.

17. The method of claim 16, wherein the first position-correcting deflector set displaces the beam on the substrate by an amount corresponding to the number of boundary regions between the respective mask subfield and the optical axis.

18. A charged particle beam pattern transfer apparatus for transferring to a substrate a pattern defined by multiple subfields on a mask, the apparatus comprising:

(a) a first main deflector set situated relative to an optical axis of the apparatus, the first main deflector set being operable to reduce off-axis aberrations;
(b) an imaging lens system operable to focus the charged particle beam deflected by the first deflector set;
(c) a second main deflector set situated relative to the optical axis, the second main deflector set being operable to reduce off-axis aberrations; and
(d) a first position-correcting deflector set situated relative to the optical axis between either the mask and the first main deflector set or the second main deflector set and the substrate, the first position-correcting deflector set being operable to deflect the charged particle beam and thus correct the position at which the charged particle beam, that has passed through a mask subfield, is incident upon the substrate so as to compensate for any discrepancies in the positions of the transfer subfields relative to each other compared to the positions of the mask subfields relative to each other.

19. The apparatus of claim 18, wherein each of the first and second main deflector sets are moving-trajectory-projection deflector sets.

20. The apparatus of claim 18, wherein the mask subfields are separated from each other by boundary regions, the first position-correcting deflector set being operable to deflect the charged particle beam in a manner whereby the boundary regions are not reproduced between transfer subfields on the substrate.

21. The apparatus of claim 18, further comprising a second position-correcting deflector set, wherein the first position-correcting deflector set is situated between the mask and the first main deflector set and the second position-correcting deflector set is situated between the second main deflector set and the substrate, the second position-correcting deflector set being operable to deflect the charged particle beam and thus correct the position at which the charged particle beam, that has passed through a mask subfield, is incident upon the substrate so as to compensate for any discrepancies in the positions of the transfer subfields relative to each other compared to the positions of the mask subfields relative to each other.

Referenced Cited
U.S. Patent Documents
5260151 November 9, 1993 Berger et al.
5466904 November 14, 1995 Pfeiffer et al.
5545902 August 13, 1996 Pfeiffer et al.
Patent History
Patent number: 5847402
Type: Grant
Filed: Dec 17, 1996
Date of Patent: Dec 8, 1998
Assignee: Nikon Corporation (Tokyo)
Inventor: Mamoru Nakasuji (Yokohama)
Primary Examiner: Bruce Anderson
Law Firm: Klarquist Sparkman Campbell Leigh & Whinston, LLP
Application Number: 8/768,201
Classifications
Current U.S. Class: 250/4922; Magnetic Lens (250/396ML); With Target Means (250/398)
International Classification: H01J 3730;